public class MyLinkLedList {
    static class ListNode{
        private int val;
        private ListNode prev;
        private ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }
    public ListNode head;
    public ListNode last;
    public int size(){
        int count=0;
        ListNode cur=head;
        while(cur!=null){
            cur=cur.next;
            count++;
        }
        return count;
    }
    public void display(){
        ListNode cur=head;
        while(cur!=null) {
            System.out.print(cur.val+" ");
            cur=cur.next;
        }
    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListNode cur=head;
        while(cur!=null){
            if(cur.val==key){
                return true;
            }
            cur=cur.next;
        }return false;
    }
    //头插法
    public void addFirst(int data){
        ListNode node=new ListNode(data);
        if(head==null){
            head=last=node;
        }else{
            node.next=head;
            head.prev=node;
            head=node;
        }
    }
    //尾插法
    public void addLast(int data){
        ListNode node=new ListNode(data);
        if(head==null){
            head=last=node;
        }else{
            node.prev=last;
            last.next=node;
            last=node;
        }

    }
    public ListNode findIndex(int index){
        ListNode cur=head;
        while(index>0){
            cur=cur.next;
            index--;
        }
        return cur;
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data) {
        if (index < 0 || index >= size()) {
            throw new posException("位置异常");
        }
        ListNode newnode = new ListNode(data);
        ListNode cur = findIndex(index);
        if (index == 0) {
            newnode.next = head;
            head = newnode;
        } else {
            newnode.next = cur;
            newnode.prev = cur.prev;
            cur.prev.next = newnode;
            cur.prev = newnode;

        }
    }
    public Boolean find(int key){
        ListNode cur=head;
        while(cur!=null){
            if(cur.val==key){
                return  true;
            }
            cur=cur.next;
        }
        return false;
    }


    //删除第一次出现关键字为key的节点
    public void remove(int key){
        if(head==null){
            System.out.println("链表为空哦不能删除");
            return ;
        }
        ListNode cur=head;
        while(cur!=null){
            if(cur.val==key){
                break;
            }
            cur=cur.next;
        }
        if(cur==head) {
            head = head.next;
            if(head!=null){
                head.prev = null;
            }else{
                last=null;
            }
        }
        else{

            if(cur.next==null){
                cur.prev.next=cur.next;
                last=last.prev;
            }else{
                cur.prev.next=cur.next;
                cur.next.prev=cur.prev;
            }

        }

    }
    //删除所有值为key的节点
    public void removeAllKey(int key){
        while(find(key)==true) {
            remove(key);
        }
    }
    //得到单链表的长度

    public void clear(){
     /*   head=null;
        last=null;*/
        ListNode cur=head;
        while(cur!=null){
            ListNode curNext=cur.next;
            cur.prev=null;
            cur.next=null;
            cur=curNext;
        }
        head=null;
        last=null;
    }

}
